Sexual maturation and morphological development of the reproductive tract in Large White and prolific Chinese Meishan pigs

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Abstract
Body weight of Large White gilts was greater at birth, weaning, 5 months of age and at slaughter; however, Meishan gilts reached puberty at an earlier age (91 .+-. 2 vs 192 .+-. 3 days, P < 0.01), had longer periods of oestrus (60 .+-. 2 vs 49 .+-. 2 h, P < 0.01) and experienced more oestrous cycles (7 .+-. 0.4 vs 4 .+-. 0.4, P < 0.01) before slaughter. The interoestrous interval was longer (P < 0.01) for Large White gilts (19.8 .+-. 0.2 vs 19.1 .+-. 0.2 days). At slaughter, uterine length (P < 0.05), uterine weight, width of uterine horns, endometrial surface area, endometrial weight and percentage of uterine weight represented by endometrium was greater (P < 0.01) for Large White gilts. However, breed differences were not significant when slaughter weight was included in analyses as a covariate. This indicated that development of the reproductive tract was proportionate to body weight at slaughter for each breed. When body weight at slaughter was included as a covariate, effects of day of the oestrous cycle and pregnancy on uterine width, uterine weight, endometrial surface area and endometrial weight were detected (P < 0.01) and for uterine length there was a day-by-status interaction (P < 0.01). Total number of CL (P < 0.05) and total ovarian weight (P < 0.05) were also greater for Large White gilts independent of body weight at slaughter. There were more CL in left ovaries for Meishan (8.1 .+-. 0.4 vs 6.6 .+-. 0.4) and Large White (8.4 .+-. 0.4 vs 7.9 .+-. 0.5) gilts. These results indicate that the more prolific Meishan gilts: (1) reach puberty at an earlier age and at a light body weight; (2) express oestrus longer and have slightly shorter oestrous cycles; (3) have morphologically smaller uteri; and (4) have lower numbers of CL in ovaries that are smaller than those of Large White gilts.